To be fair, it's completely legitimate to issue debt that the original lender can sell for liquidity, although it should probably be difficult or impossible for institutional lenders (eg credit card or mortgage) to originate those. The real problem is the combination of interest and inablity to default onto some concrete piece of collateral, which in the creditor-preferred case of making incremental payments without net reduction in the principle, amounts to fractional ownership (like owning stock in a corporation) of a person, ie slavery.